U.S. Pat. No. 7,761,480, whose disclosure is incorporated herein by reference, describes methods for information access using ontologies. As explained in this patent, an ontology is a structured vocabulary that represents the schematic metadata of a particular application domain. The ontology provides a unified, semantic model of the information in the domain, including both the types of entities that the information may include and relationships among the entities. The ontology allows users to express query concepts and relationships in high-level terms, which are then translated by appropriate agents into lower-level database schemata and semantic analyses.